Added underlyingView property to get background content from a view other than superview
Fix spinloop, updates of hidden views

Takes up much less CPU now (sleeps instead of spins when waiting for the next update)
Merge remote-tracking branch 'tleavy86/master'

Conflicts:
	FXBlurView/FXBlurView.m
Always prepare superview before snapshot; Remove superfluous parameters
Merge pull request #31 from Clinkle/master

Add underlying view (With bugfix)